A jamming device transmits an electromagnetic RF jammer signal in the form of a broad band barrage jamming signal or a sweep jammer signal into a predetermined frequency spectral range in which its targeted radio links operate. When the jammer signal is of the form of broadband barrage noise, the effect on the receiver is readily calculable. When, however, the radiated jammer signal is in the form of an instantaneous jammer signal of a given bandwidth swept across the targeted frequency spectrum, the affect on the targeted receivers has heretofore been less easy to predict. The effects of such a sweep jammer signal on a receiver depends on the electrical and physical characteristics of both the targeted receiver and the transmitted jamming signal. The various possible parameters produce a wide variety of possible affects on the targeted radio's communications ranging from no effect at all to total blockage of digital radio communications.
The main concern of both the radio operator and the jamming device operator is the effect the sweep jamming signal will have on the average link Bit Error Rate of the targeted radio link. It is therefore very desirable to those skilled in the art to be able to accurately predict the extent to which the link BER will be increased when the radio receivers are exposed to a sweep jammer signal. Such information is crucial for determining whether a given jamming device can successfully block digital radio communications (as in a combat environment).
There is presently no known process that can be used to accurately predict the affects of a sweep jammer signal on digital communications links. In fact, the few existing processes that attempt to perform this function have been shown, after being subjected to careful scrutiny in field tests, to be very inaccurate. This includes those processes currently being used in: (1) the Network Planning Terminal (NPT), (2) the Mobile Subscriber Equipment System Performance Prediction Model (MSE SPM), (3) the MOSES-I and MOSES-II (Mobile Subscriber Equipment Simulation) devices, (4) the Network Assessment Model (NAM), (5) the MSE Performance Assessment Model (MSE PAM), and (6) the Communications Electronics Warfare Model (COM EW).
One process that was examined in extensive detail was the one used in the MSE SPM model. This process, like all the others, was incorrect and very inaccurate in its calculation of the effect of the sweep jammer on the link average Bit Error Rate. The reason for this was the use of an incorrect duty cycle and an absence of an explicit dependance on the jamming signal's sweep rate necessary to compute the sweep jammer's pulse attenuation. As a result, these processes give an inaccurate prediction of the expected link BER because they fail to consider: (1) the jammer pulse is attenuated by the receiver (depending on the instantaneous sweep jammer bandwidth, sweep jammer sweep bandwidth, sweep jammer sweep rate, and receiver time constant), and (2) the net increase in the ambient background noise when the sweep jammer pulse is attenuated.
Moreover, it was noticed that the process utilized by the MSE SPM made link BER predictions that were independent of the sweep jammer's sweep rate. The other models were observed to have even poorer processes or none at all.
Consequently, those skilled in the art realize the need for a process that can provide accurate predictions for all sweep rates. Moreover, those skilled in the art realize the need for a process that can accurately perform the following functions:
1. Determine the link bit error rate for all realizations of jammer sweep rate.
2. Predict the expected BER in terms of an average BER, a peak BER, and a background BER for those cases where the sweep jammer is perceived by the receiver as being a sweep jammer or something in between being perceived as sweep jammer and a barrage jammer.
3. Determine whether a transient sweep jammer signal is perceived by the receiver as being a series of transients (occurring at the sweep rate), or a series of attenuated transients (occurring at the sweep rate) with a concurrent increase of the background noise floor, or simply an increased noise floor (a barrage jammer) because of the total inability of the receiver to follow the rise and fall of the transients produced by the sweep jammer signal.
4. Determine the net effect that a sweep jamming signal signal would have on a specific receiver based on the critical electrical and physical properties of both the jamming signal and the targeted receiver.
Accordingly, the object of this invention is to provide a process that can accurately predict a sweep jamming signal's effect on a targeted receiver in terms of the peak BER, the increased background BER, and the resultant average BER, based on the critical physical and electrical properties of the sweep jammer transmitter and its targeted digital radio receiver.
It is another object of this invention to provide a process that can determine whether a targeted receiver will perceive a sweep jamming signal as a sweep jammer, a barrage jammer, or something in between the two.